5. adsorption column design.pdf
TRANSCRIPT
-
7/29/2019 5. Adsorption Column Design.pdf
1/58
An industrial wastewater contains 10 mg/L chlorophenol, and
is going to be treated by carbon adsorption. 90% removal is
desired. The wastewater is discharged at a rate of 0.1 MGD.Calculate the carbon requirement for
a) a single , mixed contactor (CMFR)
b) two mixed (CMFR) contactors in series
c) a column contactor.
Example
0.41
q = 6.74xCFreundlich isoherm
mg/g C mg/L
-
7/29/2019 5. Adsorption Column Design.pdf
2/58
0.41q = 6.74x1 =6.74
510-1 mg/L x 3.78x10 L/d = 63.4x10 mg / day
a) Single CMFR
mg/g C
Carbon requirement =
Organic Load =
6 g C 1 kg3.4x10 mg/day x x =6.74 mg 1000 g
505 kg/day
Cinf= 10 mg/L
Ceff= 1 mg/L
-
7/29/2019 5. Adsorption Column Design.pdf
3/58
b) Two CSTRs connected in series
We assume it. It is not given in the question. If you change it,you will calculate a different value.
5 mg/L
10 mg/L
1 mg/L
-
7/29/2019 5. Adsorption Column Design.pdf
4/58
Contactor 1
Carbon requirement =
Organic Load =
Cinf= 10 mg/L
Ceff= 5 mg/L
0.41q = 6.74x5 =13.0 mg/g C
510-5 mg/L x 3.78x10 L/d = 61.89x10 mg/day
6 g C 1 kg1.89x10 mg/day x x =
13.0 mg 1000 g145 kg / day
-
7/29/2019 5. Adsorption Column Design.pdf
5/58
Contactor 2
Carbon requirement =
Organic Load =
Cinf= 5 mg/L
Ceff= 1 mg/L
mg/g C0.41q = 6.74x1 =6.74
55-1 mg/L x 3.78x10 L/d = 61.51x10 mg/day
6 g C 1 kg1.51x10 mg/day x x =
6.74 mg 1000 g224 kg/day
-
7/29/2019 5. Adsorption Column Design.pdf
6/58
0
2
4
6
8
10
12
14
16
18
20
0 1 2 3 4 5 6 7 8 9 10 11 12
qe
Ce
CoCe of 1 CMFR
and 2nd ContactorCe of 1
st Contactor
-
7/29/2019 5. Adsorption Column Design.pdf
7/58
Total C requirement = 145+224=369 kg/day
C requirement decreased because, in the 1st contactor, weare able to put more on the surface of the carbon.
a) a single , mixed contactor (CMFR)
b) two mixed (CMFR) contactors inseries
-
7/29/2019 5. Adsorption Column Design.pdf
8/58
-
7/29/2019 5. Adsorption Column Design.pdf
9/58
Concentration (mg/L)
Column
Height
FlowDirection
0 Co
Here you start observing your breakthrough curvewhen the last layer starts getting saturated.
Everything happens in the primaryadsorption zone (or mass transferzone, MTZ). This layer is in contact with
the solution at its highestconcentration level, C
o. As time
passes, this layer will start saturating.
Whatever escapes this zone will than be
trapped in the next zones. As the
polluted feed water continues to flow
into the column, the top layers of carbon
become, practically, saturated withsolute and less effective for further
adsorption. Thus the primary adsorption
zone moves downward through the
column to regions of fresher adsorbent.
-
7/29/2019 5. Adsorption Column Design.pdf
10/58
Flow
Direction
0 Co
Last primary adsorption zone. It is called
primary because the upper layers are
not doing any removal job. They aresaturated.
When breakthrough occurs there is someamount of carbon in the column still not used.
Generally, this is accepted to be 10-15%.
-
7/29/2019 5. Adsorption Column Design.pdf
11/58
Primary adsorption zone
Region where the solute is most effectively
and rapidly adsorbed.
This zone moves downward with a constantvelocity as the upper regions become
saturated.
-
7/29/2019 5. Adsorption Column Design.pdf
12/58
Ref: http://web.deu.edu.tr/atiksu/ana07/arit4.html
Active zones at various times during adsorption and thebreakthrough curve..
http://web.deu.edu.tr/atiksu/ana07/arit4.htmlhttp://web.deu.edu.tr/atiksu/ana07/arit4.html -
7/29/2019 5. Adsorption Column Design.pdf
13/58
Column Contactor
Organic Load =
Cinf= 10 mg/L
Ceff= 1 mg/L
mg/g C0.41q = 6.74x10 =17.3
510-1 mg/L x 3.78x10 L/d = 63.4x10 mg/day
6 g C 1 kg 100%3.4x10 mg/day x x x =17.3 mg 1000 g 90%
218.4 kg/day
Carbon requirement =
Assume that the breakthrough occurs while 10%of the carbon in the column is still not used.
-
7/29/2019 5. Adsorption Column Design.pdf
14/58
Packed Column Design
It is not possible to design a column accurately without a
test column breakthrough curve for the liquid of interest
and the adsorbent solid to be used.
breakthrough curve
-
7/29/2019 5. Adsorption Column Design.pdf
15/58
Theoretical Breakthrough Curve
-
7/29/2019 5. Adsorption Column Design.pdf
16/58
Packed Column Design
i. Scale up procedure
and
ii. Kinetic approach
are available to design adsorption columns . Inboth of the approaches a breakthrough curve
from a test column, either laboratory or pilot
scale, is required, and the column should be as
large as possible to minimize side wall effects.Neither of the procedures requires the adsorption
to be represented by an isotherm such as the
Freundlich equation.
-
7/29/2019 5. Adsorption Column Design.pdf
17/58
Packed Column Design
Use a pilot test column filled with the carbon to be
used in full scale application.
Apply a filtration rate and contact time (EBCT)
which will be the same for full scale application (to
obtain similar mass transfer characteristics).
Obtain the breakthrough curve.
Work on the curve for scale up.
Scale up Procedure for Packed Columns
-
7/29/2019 5. Adsorption Column Design.pdf
18/58
An industrial wastewater having a TOC of 200 mg/L will be
treated by GAC for a flowrate of 150 m3
/day. Allowable TOCin the effluent is 10 mg/L.
Pilot Plant Data
Q = 50 L/hr
Column diameter = 9.5 cm
Column depth (packed bed) = 175 cm
Packed bed carbon density = 400 kg/m3
Vbreakthrough = 8400 L
Vexhaustion = 9500 L
Example
-
7/29/2019 5. Adsorption Column Design.pdf
19/58
Breakthrough Curve of the Pilot Plant
-
7/29/2019 5. Adsorption Column Design.pdf
20/58
a) Filtration rate of the pilot plant
3
2
Q L 1 1000cm= 50 x x =
A hr 1Ld
2
3
2
cm705
hr.cmFR =
d = 9.5 cm
The same FR applies to Packed Column.
-
7/29/2019 5. Adsorption Column Design.pdf
21/58
b) Area of the Packed Column
FR =Q
A
QA =
FR
3 2 6 3
3 3
2m 1 h.cm 1 d 10 cmA = 150 x . x x =
d 705 cm 24 h 1 m
8865cm
4 x 8865d= =
106cm
-
7/29/2019 5. Adsorption Column Design.pdf
22/58
c) Empty Bed Contact Time of the Pilot Plant
15 mins.is the EBCT of the Packed Column.
=
Q
2 2
3d 9.5
= A x Height = x H = 3.14 x x175 = 12,404 cm =2 2
12.4 L
12.4 L = = 0.248 hr = 14.88
50 L/hr 15 min
-
7/29/2019 5. Adsorption Column Design.pdf
23/58
d) Height of the Packed Column
The same as the height of the Pilot Plant. Because height
is set by and , and these are the same for Pilot
Plant and the Packed Column.
3
2
Q cm 1 hr x = 15 min x 705 x =
A hr.cm 60 min
176 cm
Q/A
-
7/29/2019 5. Adsorption Column Design.pdf
24/58
e) Mass of Carbon required in the Packed Column
2= 1.76 m x x 1.06 =4
31.553 m
density = 400 kg/m3
3
3
kg
1.553 m x 400 =m 621 kg
Packed bed carbon density is given by the supplier.
-
7/29/2019 5. Adsorption Column Design.pdf
25/58
f) Determination of qe
Mass of carbon in the pilot column =
x density3
3
kg
= 0.0124 m x 400 = 4.96m 5 kg
TOC removed by 5 kg of carbon =
200 mg/L x 9500 L = 61.9x10 mg
6
e
1.9x10 mg TOCq = =
5 kg C
mg380 C
g
Volume of the pilot column = 12.4 L
-
7/29/2019 5. Adsorption Column Design.pdf
26/58
g) Fraction of Capacity Left Unused (Pilot Plant)
Fraction of capacity left unused = f =
Total capacity = mg
9500 L x 200 =L
61.9x10 mg
TOC removed before breakthrough =
mg
8400 L x 200 =L
61.68x10 mg
6
61.9-1.68 x10 x100
1.9x10 12%
This fraction of capacity left unused will apply to the
Packed Column also.
-
7/29/2019 5. Adsorption Column Design.pdf
27/58
The same as the Packed Column :
6 mg 130x10 x =d 380 mg/g C
78.9 kg/d
Amount of carbon consumed =
Organic Loading =
Carbon consumption rate =
h) Breakthrough time of the Packed Column
3
3
mg m 1000 L200 x 150 x =
L d 1 m
630x10 mg/d
621 kg x 1-0.12 = 546.5 kg
Breakthrough time =546.5 kg
78.9 kg/d
7 days
1 hr 1 d8400 L x x =50 L 24 hr
7 days
-
7/29/2019 5. Adsorption Column Design.pdf
28/58
-
7/29/2019 5. Adsorption Column Design.pdf
29/58
i) Volume Treated Before Breakthrough
3
treated
m= 150 x 7 days =
d 31050 m
-
7/29/2019 5. Adsorption Column Design.pdf
30/58
Packed Column Design
This method utilizes the following kinetic equation.
Kinetic Approach
1 o ok
q M - C Vo Q
C 1
C
1 + e
-
7/29/2019 5. Adsorption Column Design.pdf
31/58
where
C = effluent solute concentration
Co = influent solute concentration
k1 = rate constant
qo = maximum solid phase concentration of
the sorbed solute, e.g. g/g
M = mass of the adsorbent. For example, g
V = throughput volume. For example, liters
Q = flow rate. For example, liters per hour
-
7/29/2019 5. Adsorption Column Design.pdf
32/58
Packed Column Design
Kinetic Approach
The principal experimental information required is
a breakthrough curve from a test column, eitherlaboratory or pilot scale.
One advantage of the kinetic approach is that the
breakthrough volume, V , may be selected in the
design of a column.
-
7/29/2019 5. Adsorption Column Design.pdf
33/58
Packed Column Design
Assuming the left side equals the rigth side,
cross multiplying gives
Rearranging and taking the natural logarithms ofboth sides yield the design equation
t o ok
q M - C VQ oC
1 + e = C
-
7/29/2019 5. Adsorption Column Design.pdf
34/58
Packed Column Design
Rearranging and taking the natural logarithms of
both sides yield the design equation.
o 1 o 1 o
C k q M k Cln -1 = -C Q Q
V
y = b - mx
-
7/29/2019 5. Adsorption Column Design.pdf
35/58
A phenolic wastewater having a TOC of 200 mg/L is to be
treated by a fixed
bed granular carbon adsorption columnfor a wastewater flow of 150 m3/d, and the allowable
effluent concentration, Ca, is 10 mg/L as TOC. A
breakthrough curve has been obtained from an
experimental pilot column operated at 1.67 BV/h. Other
data concerning the pilot column are as follows:inside diameter = 9.5 cm , length = 1.04 m,
mass of carbon = 2.98 kg , liquid flowrate = 12.39 L/h ,
unit liquid flowrate = 0.486 L/s.m2 , and
the packed carbon density = 400 kg/m3
.The design column is to have a unit liquid flowrate of 2.04
L/s.m2 , and the allowable breakthrough volume is 1060 m3.
Example
-
7/29/2019 5. Adsorption Column Design.pdf
36/58
Using the kinetic approach for design, determine :
The design reaction constant, k1 , L/s-kg.
The design maximum solid - phase concentration,
qo , kg/kg.
The carbon required for the design column, kg. The diameter and height of the design column, m.
The kilograms of carbon required per cubic meter
of waste treated.
Example
-
7/29/2019 5. Adsorption Column Design.pdf
37/58
V (L) C(mg/L) C/Co Co/C Co/C-1 ln(Co/C-1)
0 0 0,000
378,0 9 0,045 22,222 21,222 3,06
984,0 11 0,055 18,182 17,182 2,84
1324,0 8 0,040 25,000 24,000 3,18
1930,0 9 0,045 22,222 21,222 3,06
2272,0 30 0,150 6,667 5,667 1,73
2520,0 100 0,500 2,000 1,000 0,00
2740,0 165 0,825 1,212 0,212 -1,55
2930,0 193 0,965 1,036 0,036 -3,32
3126,0 200 1,000 1,000 0,000
-
7/29/2019 5. Adsorption Column Design.pdf
38/58
0
20
40
60
80
100
120
140
160
180
200
0 500 1000 1500 2000 2500 3000 3500
C,mg/L
V, Liters
-
7/29/2019 5. Adsorption Column Design.pdf
39/58
-9
-4
1
6
11
16
0 1000 2000 3000 4000
ln(Co/C-1)
V (L)
Plot of Complete Data Set
-
7/29/2019 5. Adsorption Column Design.pdf
40/58
Take the linear range only!
y = -0,0064x + 15,787
-5
0
5
10
15
0 1000 2000 3000 4000
ln(Co/C-1)
Volume treated (L)
-
7/29/2019 5. Adsorption Column Design.pdf
41/58
q k M0 115.787=
Q
k C-1 1 00.0064L =
Q
-4
L-1(0.0064L ) (12.39 )Lha)k = =3.96 10mg1 mg h200
L
-4610 mgL 1h L3.96 10 =0.11
3600smg h 1kg kg s
-
7/29/2019 5. Adsorption Column Design.pdf
42/58
Lq 0.11 2.98kg0 kg sb)15.787=
L 1h12.39 3600sh
L 1h15.787 12.393600shq =
0 L0.11 2.98kgkg s
kgq =0.166
0 kg
Q 6250 L / hL
-
7/29/2019 5. Adsorption Column Design.pdf
43/58
Q = 6250 L / h
kgq =0.1660 kg
4 Lk =3.96 101 mg h
V =1050000 L
0C = 200 mg / L
o 1 o 1 oC k q M k Cln -1 = -C Q Q
V
Using
4 43.96 10 0.166 3.96 10 200 1050000
200ln -1 = -
10 6250 6250
ML kg L mg
Lmg h kg mg h L
L Lh h
M=1545009487 mg =1545 kg
-
7/29/2019 5. Adsorption Column Design.pdf
44/58
Q = 6250 L / h = 1.736 L / s
M =1545 kg
2Unit liquid flowrate = 2.04 L / s m (given)
Then, design bed volume is;
3Packet carbon density = 400 kg / m (given)
3
3
15453.86 m
400
kgV
kg
m
2
2
1.736 L / sCross section area = 0.85m
2.04 L / s m
3
2
3.86 mColumn height = 4.54 m
0.85 md = 1.04 m
3
B 3
1050 mT = 7 d
150 m / dBreakthrough time is;
Scale p approach
-
7/29/2019 5. Adsorption Column Design.pdf
45/58
3 3M = BV = 3.74 m 400 kg / m =1500 kg
Scale-up approach:
3
t 3
150 m / d kg 1000 LM = 8.954 kg/h
24 h 698 L m
1. The design bed volume (BV) is found as;
33150 /
1.67 BV / h = = 6.25 m / h24 /
m d
h d
3BV = 3.74 m
2. The mass of carbon required is;
From the breakthrough curve the volume treated at the allowablebreakthrough (10 mg/L TOC) is 2080 L. So, the solution treated perkilogram of carbon is 2080 L/2.98 kg or 698 L/kg (pilot scale). The same
applies to the design column; for a flow rate of 150 m3/d.
3. The weight of carbon exhausted per hour (Mt) is
-
7/29/2019 5. Adsorption Column Design.pdf
46/58
0
20
40
60
80
100
120
140
160
180
200
0 500 1000 1500 2000 2500 3000 3500
C,mg/L
V, Liters
-
7/29/2019 5. Adsorption Column Design.pdf
47/58
3 3
B
V = Q T =150 m / d 7 d = 1050 m
4. The breakthrough time is;
1500 kg
T = =168 h = 7 d8.954 kg / h
5. The breakthrough volume of the design column is;
Comparing the results of two approaches:
M=1545 kg
Kinetic approach Scale-up approach
M = 1500 kg3
BV = 1050 m
BT = 7 d
3
BV = 1050 m
BT = 7 d3
DesignV = 3.86m3
DesignV = 3.74m
E l
-
7/29/2019 5. Adsorption Column Design.pdf
48/58
A phenolic wastewater that has phenol concentration of 400
mg/L as TOC is to be treated by a fixedbed granular
carbon adsorption column for a wastewater flow of 227100
L/d, and the allowable effluent concentration, Ca, is 35 mg/L
as TOC. A breakthrough curve has been obtained from an
experimental pilot column operated at 1.67 BV/h. Other
data concerning the pilot column are as follows:inside diameter = 9.5 cm , length = 1.04 m,
mass of carbon = 2.98 kg , liquid flowrate = 17.42 L/h ,
unit liquid flowrate = 0.679 L/s.m2 , and
the packed carbon density = 401 kg/m3
.The design column is to have a unit liquid flowrate of 2.38
L/s.m2 , and the allowable breakthrough volume is 850 m3.
Example
-
7/29/2019 5. Adsorption Column Design.pdf
49/58
V(L)
C(mg/L) C/Co Co/C Co/C - 1 ln(Co/C - 1)
15 12 0.030 33.333 32.333 3.476
69 16 0.040 25.000 24.000 3.178
159 24 0.060 16.667 15.667 2.752
273 16 0.040 25.000 24.000 3.178
379 16 0.040 25.000 24.000 3.178
681 20 0.050 20.000 19.000 2.944
965 28 0.070 14.286 13.286 2.587
1105 32 0.080 12.500 11.500 2.442
1215 103 0.258 3.883 2.883 1.059
1287 211 0.528 1.896 0.896 -0.110
1408 350 0.875 1.143 0.143 -1.946
1548 400 1.000 1.000 0.000
-
7/29/2019 5. Adsorption Column Design.pdf
50/58
0
50
100
150
200
250
300
350
400
0 200 400 600 800 1000 1200 1400
C,
mg/L
V, Liters
-
7/29/2019 5. Adsorption Column Design.pdf
51/58
-3
-2
-1
0
1
2
3
4
0 200 400 600 800 1000 1200 1400 1600
ln
(Co/C-1)
V (L)
-
7/29/2019 5. Adsorption Column Design.pdf
52/58
y = -0,0146x + 18,657R = 0,9972
-3
-2
-1
0
1
2
3
1050 1150 1250 1350 1450
ln(C
o/C-1)
V (L)
q k M
-
7/29/2019 5. Adsorption Column Design.pdf
53/58
q k M0 118.657=
Q
k C-1 1 00.0146 L = Q
-4
L-1(0.0146 L ) (17.42 )L Lhk = =6.36 10 0.177
mg1 mg h kg s400 L
L 1h18.657 17.423600shq =
0 L0.177 2.98kgkg s
kgq =0.1710 kg
Q = 9462 5 L / h4 Lk 6 36 10
-
7/29/2019 5. Adsorption Column Design.pdf
54/58
Q = 9462.5 L / h
kgq =0.1710 kg
4 Lk =6.36 101 mg h
V = 850000 L
0C = 400 mg / L
o 1 o 1 oC k q M k C
ln -1 = -C Q Q
V
Using
4 46.36 10 0.171 6.36 10 400 850000
400ln -1 = -
35 9462.5 9462.5
ML kg L mg
Lmg h kg mg h L
L Lh h
M=2190 kg
M 2190 kg
-
7/29/2019 5. Adsorption Column Design.pdf
55/58
Q = 9462.5 L / h = 2.63 L / s
M =2190 kg
2Unit liquid flowrate = 2.38 L / s m (given)
Then, design bed volume is;
3Packet carbon density = 401 kg / m (given)
3
3
21905.46 m
401
kgV
kg
m
2
2
5.46 L / sCross section area = 2.29m
2.38 L / s m
3
2
5.46 mColumn height = 2.38 m
2.29 md = 1.71 m
3
B 3
850 mT = 3.74 d
227.1 m / dBreakthrough time is;
Scale-up approach:
-
7/29/2019 5. Adsorption Column Design.pdf
56/58
3 3M = BV = 5.67 m 401 kg / m = 2272 kg
Scale-up approach:
t
227100 L / d kgM = 25.4 kg/h
24 h /d 372.5 L
The design bed volume (BV) is found as;
227100 /1.67 BV / h = = 9462.5 L / h24 /
L d
h d
3BV = 5666.17 L = 5.67 m
The mass of carbon required is;
From the breakthrough curve the volume treated at the allowable
breakthrough (35 mg/L TOC) is 1110 L. So, the solution treated per
kilogram of carbon is 1110 L/2.98 kg or 372.5 L/kg (pilot scale).
The same applies to the design column; for a flow rate of 227100L/d, the weight of carbon exhausted per hour (Mt) is
105
-
7/29/2019 5. Adsorption Column Design.pdf
57/58
0
35
70
105
0 111 222 333 444 555 666 777 888 999 1110 1221
C,
mg/L
V, Liters
-
7/29/2019 5. Adsorption Column Design.pdf
58/58
3 3
B
V = Q T = 227.1 m / d 3.73 d = 846.5 m
The breakthrough time is;
2272 kg
T = = 89.5 h = 3.73 d25.4 kg / h
The breakthrough volume of the design column is;
M=2190 kg
Kinetic approach Scale-up approach
M = 2272 kg
3
BV = 846.5 m
BT = 3.73 d
3
BV = 850 m
BT = 3.74 d3
D iV = 5.46m3
D iV = 5.67m
Comparing the results of two approaches: